The present invention relates to an exhaust apparatus equipped with an exhaust pressure adjusting unit capable of adjusting the opening area of an exhaust pipe variably, a semiconductor device manufacturing system having the exhaust apparatus and a method for manufacturing a semiconductor device employing the semiconductor device manufacturing system.
Conventionally, in semiconductor device manufacturing process steps such as a cleaning step and an etching step, by using such chemicals as sulfuric acid (H2SO4), hydrofluoric acid (HF), aqueous hydrogen peroxide (H2O2), ammonia water (NH4OH) and hydrochloric acid (HCl), the surface processing such as a cleaning of semiconductor wafers and an etching of such material as a silicon oxide film and/or a photoresist film formed on a semiconductor wafer have been performed.
A cleaning apparatus and an etching apparatus that use the above-stated chemicals are equipped with an exhaust pipe connected to an exhaust duct to prevent such resultant gas mixture as harmful gas generated from the chemicals from leaking into a clean room, while preventing dust from adhering to the surface of a semiconductor wafer. That is, the apparatuses are configured so that the resultant gas is forcibly exhausted outside a clean room via the exhaust pipe and the exhaust duct.
FIG. 5 is a block diagram illustrating the configuration of a conventional cleaning apparatus. This cleaning apparatus comprises a cleaning processing unit 51 for cleaning semiconductor wafers, a chemical storage unit 52 consisting of chemical feed tanks 52a, 52b, 52c and 52d for storing such chemicals as sulfuric acid, hydrofluoric acid, aqueous hydrogen peroxide, ammonia water and hydrochloric acid, respectively, a waste liquid collection unit 53 for collecting waste liquid generated after usage of chemicals in the cleaning processing unit 51 in accordance with the classification of the waste liquid, an exhaust processing unit 54 for exhausting such resultant gas mixture as harmful gas generated from the cleaning processing unit 51, and a control unit 55 for controlling respective equipments disposed in the cleaning processing unit 51, the chemical storage unit 52, the waste liquid collection unit 53 and the exhaust processing unit 54.
The cleaning processing unit 51 is in flow communication with a pure water supply pipe 56 for supplying pure water and a gas introduction pipe 57 for introducing nitrogen gas via switching valves 62 and 63, respectively. In addition, the chemical feed tanks 52a, 52b, 52c and 52d are in flow communication on feed sides with the cleaning processing unit 51 via chemical supply pipes 59a, 59b, 59c and 59d, respectively, on which switching valves 58a, 58b, 58c and 58d are mounted respectively.
Furthermore, the waste liquid collection unit 53 is provided with a drain line 61 to collect the waste liquid and the drain line 61 is provided with branch pipes to collect the waste liquid in accordance with the classification of the waste liquid, and switching valves 60a, 60b, 60c and 60d are mounted on the branch pipes, respectively. Note that the branch pipes are connected to liquid drainage pipes (not shown) respectively to drain the waste liquid outside a clean room.
The exhaust processing unit 54 comprises a main exhaust pipe 54a having a flow communication portion connected to the cleaning processing unit 51, an exhaust distributing unit 54b provided on the end portion of the main exhaust pipe 54a, and an alkaline exhaust pipe 54c and an acid exhaust pipe 54d extending from the exhaust distributing unit 54b. The alkaline exhaust pipe 54c and the acid exhaust pipe 54d are provided with exhaust pressure adjusting units 64a and 64b, respectively, capable of adjusting the opening area of the exhaust pipe variably. In addition, the end portions of the alkaline exhaust pipe 54c and the acid exhaust pipe 54d are connected to exhaust ducts (not shown) respectively for exhausting exhaust gas forcibly outside a clean room.
The operation of the cleaning apparatus having the above-described configuration will be explained below. For example, the operation for cleaning semiconductor wafers with a mixture of sulfuric acid and aqueous hydrogen peroxide is described as follows: first, semiconductor wafers to be cleaned are loaded into the cleaning processing unit 51; and then in the chemical storage unit 52, the switching valves for the chemical feed tanks storing sulfuric acid and aqueous hydrogen peroxide are opened by the control unit 55; and simultaneously in the waste liquid collection unit 53, the switching valve for collecting the mixture of sulfuric acid and aqueous hydrogen peroxide is opened; furthermore, in the exhaust processing unit 54, the alkaline exhaust pipe 54c is closed by the exhaust pressure adjusting unit 64a to enter closed status and the acid exhaust pipe 54d is opened by the exhaust pressure adjusting unit 64b to enter opened status; accordingly, resultant acid gas generated from the mixture of sulfuric acid and aqueous hydrogen peroxide is forcibly exhausted into an acid processing apparatus located outside a clean room via the acid exhaust pipe 54d and the exhaust duct.
However, there has been seen a problem that the resultant gas to be exhausted leaks from respective rotating shaft takeoff connections of the exhaust pressure adjusting units 64a and 64b, which are provided in the alkaline exhaust pipe 54c and the acid exhaust pipe 54d of the exhaust processing unit 54, respectively, resulting in the exhaust gas leakage from the exhaust pipes.
FIG. 6 is a sectional view of the exhaust apparatus equipped with the conventional exhaust pressure adjusting unit 64a or 64b shown in FIG. 5. That is, FIG. 6 illustrates a configuration of the exhaust apparatus used both in the alkaline exhaust pipe 54c and the acid exhaust pipe 54d. The exhaust apparatus comprises a disc-shaped switching valve 72 having a diameter approximately equal to the inner diameter of an exhaust pipe 70, a rotating shaft 71 for rotating the switching valve 72 and fixing screws 73 for fixing the switching valve 72 along a diameter of the shaft to the rotating shaft 71. As described above, the switching valve 72 is configured to be rotatable on the shaft passing along the diameter of the valve. In addition, one end portion 71a of the rotating shaft 71 is inserted into a concave rotating shaft bearing portion 70a formed in the exhaust pipe 70 and the other end portion 71b of the rotating shaft 71 is taken out of the exhaust pipe 70 to the outside of the pipe through the cylinder-shaped rotating shaft takeoff connection 70b formed in the exhaust pipe 70. That is, the disc-shaped switching valve 72 and the rotating shaft 71 are supported rotatably by the rotating shaft bearing portion 70a and the rotating shaft takeoff connection 70b, and thus the amount of exhaust gas to be exhausted can be adjusted variably in accordance with the rotated position of the switching valve 72. In the other end portion 71b of the rotating shaft 71, an airtight O-ring 74 for preventing exhaust gas to be exhausted from leaking and a groove (not shown) for the airtight O-ring 74 to be fixed thereto are provided.
In the exhaust apparatus configured in this manner, the internal pressure of the exhaust pipe 70 is lower than the atmospheric pressure in the usual condition since the gas included in the pipe is sucked by the exhaust fan installed outside and therefore, the resultant gas mixture (exhaust gas) to be exhausted never leaks outside from the exhaust pipe 70. However, for example, many semiconductor device manufacturing systems are connected to the exhaust duct, which is in flow communication with the exhaust fan on one end, and when simultaneous running of these semiconductor device manufacturing systems requires the exhaust fan to exhaust larger amount of gas than the exhausting capacity of the fan, the internal pressure of the exhaust pipe 70 becomes higher than the atmospheric pressure in some cases. In this case, micro gap is formed along the circumference of the airtight O-ring 74 for the following reason. That is, although the airtight O-ring 74 is disposed to fill the gap 75 between the rotating shaft takeoff connection 70b of the exhaust pipe 70 and the rotating shaft 71, the O-ring is not capable of sealing the internal space of the exhaust pipe 70 completely. Therefore, the exhaust gas to be exhausted is in danger of leaking outside the exhaust pipe 70 via the micro gap when the internal pressure of the exhaust pipe 70 becomes higher than the atmospheric pressure.